Diversity

There are 7 extant species of tarsiers, all in the genus Tarsius. Tarsier species are all similar in size, morphology, and ecology. They are all small, nocturnal, predaceous primates specialized for leaping and clinging. Tarsiers are the most "primitive" of the haplorrhine primates, with fossils dating to the Eocene. They were once widely distributed, fossils are known from North America, Europe, North Africa, and Asia. (Niemitz, 2003)

Geographic Range

Tarsiers are found only in archipelagos in southeast Asia, including Sumatra, Borneo, Sulawesi, and parts of the Philippine Islands. (Niemitz, 2003)

Habitat

Tarsier species are all highly arboreal and are found primarily in tropical, forested habitats with dense vertical growth. They use leaping between vertical tree trunks or other vertical supports extensively to get around and this is an important component of their habitats. They may venture into non-forested habitats if there are sufficient vertical surfaces for clinging and leaping. They will jump to the ground to move around as well, but will only remain on the ground momentarily. Sleeping roosts in trees, hollows, and clusters of vines are also important components of their habitats. Most of their foraging time is spent below 1 m in the vertical structure of a forest. Sleeping roosts are mainly at 2 to 5 meters above the ground. (Niemitz, 2003)

Physical Description

Tarsiers are small primates, weighing 80 to 150 g. Their fur is velvety or silky and buff, grayish brown, or dark brown on the back and grayish or buffy on the underside, generally resembling the color of dead leaves or bark. Species from higher altitudes sometimes have curly hair. Their most distinctive features are their round heads, remarkably large eyes that are directed forward, and their medium to large, hairless, and very mobile ears. Their eyes are so large that one of them weighs nearly as much as their brain. The skin in relatively naked areas of the body are often colored by glandular secretions. Males of some species have orange on the skin near their testicles and other species have dark brown spots on their ears. Their muzzle is short, and they seem to have almost no neck (although they are capable of turning their head over 180 degrees!). Tarsiers have long, slender bodies, but tend to look round because of their habit of crouching while clinging to a branch. Body lengths are up to 10 cm. Like all haplorrhines, tarsiers have hairs on their nose pads. There is little to no sexual dimorphism, although males may be slightly larger. (Feldhamer, et al., 1999; Groves, 1989; Niemitz, 2003; Nowak and Paradiso, 1983; Szalay and Delson, 1979; Thorington and Anderson, 1984; Vaughan, 1986; Vaughan, et al., 2000)

Tarsier forelimbs are short and their hindlimbs elongated, the hindlimbs are longer in proportion to body length than in any other mammal. They are unique among mammals in that the elongation of their hindlimbs is the result of lengthening of the tarsals (especially the calcaneum and navicular) rather than the metatarsals. By elongating the tarsals, tarsiers can lengthen the limbs without sacrificing dexterity of the hands, often a result of metatarsal elongation. The elongation of their tarsals gives their names "Tarsiidae" or "Tarsius". The digits are extraordinarily long and tipped with soft, rounded toe pads that help them grip and cling to surfaces. The pollex is not opposable, but the hallux is. All digits have flattened nails except the second and third hind toes, which have claw-like nails used for grooming (sometimes called "toilet claws"). The tail is naked except for tufts of hairs at the tip and is thin and long, from 20 to 25 cm. Tarsier species have ridges of skin on the ventral surfaces of their tail that help them to stabilize themselves against tree trunks when clinging. (Feldhamer, et al., 1999; Groves, 1989; Niemitz, 2003; Nowak and Paradiso, 1983; Szalay and Delson, 1979; Thorington and Anderson, 1984; Vaughan, 1986; Vaughan, et al., 2000)

Reproduction

In species for which information is available, male tarsiers generally have larger home ranges that overlap with those of several females. Males may also rest during the day in the company of one or several females. Some evidence also suggests that a portion of males are not reproductively active and may represent "spare" males that cannot compete with dominant, reproductively active males. Social group members may help to care for offspring. (Niemitz, 2003; Nowak and Paradiso, 1983; Vaughan, 1986; Vaughan, et al., 2000)

Most tarsier species seem to reproduce seasonally. Some species may reproduce throughout the year, but most births are concentrated seasonally. Tarsiers give birth to a single young after a gestation period of about 6 months. Tarsier young weigh 25 to 30% of their mother's body weight, the largest young relative to maternal body mass in mammals. There is little information on reproduction in some tarsier species. In the few species for which there is information, births peak or occur at the end of the rainy season (generally between February and July, varying regionally). (Niemitz, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Females invest heavily in their single offspring through gestation and lactation. Young are born at a precocial stage, able to cling and climb on the day of their birth. In some species the young are cared for by their mother as well as the dominant male of the group and subadult or secondary females. Information on parental investment in most species is lacking. Young may associate with their parents for a period of time after weaning. (Niemitz, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Lifespan/Longevity

Tarsiers can live up to 16 years, although there is little data on wild lifespan for most species. (de Magalhães, 2009)

Behavior

All tarsier species are nocturnal or crepuscular. Most species live in small social groups, sometimes of just a single male and female but often consisting of a single, dominant male, several females, and their dependent young. Western tarsiers (Tarsius bancanus) seem to be more solitary. Tarsiers are mainly seen alone during their active, nocturnal phase, but often sleep with other individuals during the day, although some species rest alone as well. Social groups and individuals defend territories with scent marking and vocalizations. Scent marks can be quite consistent in some species, indicating very stable home ranges. Males generally have larger home ranges that overlap with those of several females. When social groups get together, they may spend time grooming each other. (Niemitz, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Tarsiers are extremely specialized for vertical clinging and leaping. Their rigid tails with ventral ridges help them to cling to vertical supports. Their extremely elongated hindlimbs, well-developed leg muscles (thigh muscles may represent 12% of total body mass), and long fingers with gripping tips enable them to make impressive leaps of up to 45 times their body length. They are especially adept at backward leaping, propelling themselves backwards, rotating in the air, and landing with their feet. They also use quadrupedal locomotion, small hops, and can run on their hindlimbs on the ground. (Niemitz, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Communication and Perception

Tarsiers use scent marking and vocalizations to mark and defend territories and to confirm group membership. Scent marking is through urine and gland secretions deposited onto objects in their environment. Glands are on their lips, chest, and anogenital region. Individuals may vocalize, often at dawn and dusk, but duetting or chorusing is also common among members of social groups. Vocalizations at dawn and dusk may represent times when individuals are departing from or arriving at communal resting areas. The majority of their nocturnal foraging time may be spent alone. Some species are relatively silent except for inter-individual contact calls. (Niemitz, 2003; Nowak and Paradiso, 1983; Vaughan, et al., 2000)

Food Habits

Tarsier species eat only animal prey. They use their exceptional vision and hearing at night to detect prey and their agile, rapid leaps to grab prey up to their own size. Their primary prey are arthropods, especially moths and butterflies, orthopterans, ants, and beetles, but they also eat birds, lizards, and snakes. In most species, foraging occurs most at less than 1.5 meters from the ground. In Tarsius tarsier the majority of prey are caught on branches or leaves (~60%) or in the air (~25%). Only about 5% of prey are caught on the ground. (Niemitz, 2003; Vaughan, et al., 2000)

Predation

Tarsiers may fall prey to any number of arboreal, nocturnal predators that share their tropical, forested habitats. They have been observed mobbing and being captured by snakes and a slow loris (Nycticebus). Their nocturnal habits, exceptionally keen vision and hearing, and their agility protect them from predation to some extent. Their habit of clinging to vertical surfaces makes it more difficult for most animals to capture them. (Niemitz, 2003)

Ecosystem Roles

Tarsier species are important predators of arthropod prey and other animals in their tropical forest habitats. They show remarkable convergences with owls and effectively occupy a similar niche. Over 30 convergences have been noted between owls and tarsiers, including external morphology, characteristics of their inner ears, and their ecology. They are host to a diverse fauna of endoparasites. (Niemitz, 2003)

Economic Importance for Humans: Positive

Tarsiers are generally too small to be hunted for food. They are fascinating primates, providing perspectives on the evolution of their unique locomotion style and life histories. Their nocturnal habits make them difficult to observe, so ecotourism opportunities are limited. However, tarsiers are efficient predators of large arthropods, many of which are crop pests, so help to control their populations. (Niemitz, 2003)

Positive Impacts

controls pest population

Economic Importance for Humans: Negative

There are no adverse effects of tarsiers on humans.

Conservation Status

The IUCN recognizes 8 species of tarsiers, including the newly named Lariang tarsier (Tarsius lariang, 2006). Two species are considered endangered, three are considered vulnerable, 1 is near threatened, and 2 are data deficient. All tarsier species are considered threatened by habitat destruction of 30% or more throughout their range and continued taxonomic uncertainty makes assessing risks difficult. In appropriate, primary forest habitat tarsier species can be common, but they become more rare in degraded habitat. They may be negatively impacted by human use of insecticides in some areas. (IUCN, 2009; Niemitz, 2003)

Other Comments

Contributors

Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

acoustic

uses sound to communicate

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

cooperative breeder

helpers provide assistance in raising young that are not their own

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

duets

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

insectivore

An animal that eats mainly insects or spiders.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

polygynous

having more than one female as a mate at one time

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

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Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.